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PHP中遇到BOM、<feff>编码导致json_decode函数无法解析问题

Jun 13, 2016 am 09:32 AM
bom decode json php

昨天同事遇到一个奇怪的问题,就是以下代码,无法通过JSON校验,也无法通过PHP的json_decode函数解析。

复制代码 代码如下:


[
    {
        "title": "",
        "pinyin": ""
    }
]


可能聪明的你已经猜到其中包含有不看见的特殊字符,在vim下查看:

复制代码 代码如下:


[
    {
        "title": "",
        "pinyin": ""
    }
]


发现在“title”前面有一个字符,如果你之前了解过BOM,应该知道这个特殊字符就是BOM,关于其介绍可以参考另一篇文章:计算机中的字符串编码、乱码、BOM等问题详解.


在Linux下通过xxd命令查看文件内容的十六进制:

复制代码 代码如下:


0000000: 5b 0a 20 20 20 20 7b 0a 20 20 20 20 20 20 20 20  [.    {.       
0000010: ef bb bf 22 74 69 74 6c 65 22 3a 20 22 22 2c 0a  ..."title": "",.
0000020: 20 20 20 20 20 20 20 20 22 70 69 6e 79 69 6e 22          "pinyin"
0000030: 3a 20 22 22 0a 20 20 20 20 7d 0a 5d 0a           : "".    }.].


可以看到刚才那个"title"前面的特殊字符十六进制为:ef bb bf,正是标记UTF-8的BOM。BOM的含义如下:

复制代码 代码如下:


开头字节            Charset/encoding
EF BB BF        UTF-8
FE FF           UTF-16/UCS-2, little endian(UTF-16LE)
FF FE           UTF-16/UCS-2, big endian(UTF-16BE)
FF FE 00 00     UTF-32/UCS-4, little endian.
00 00 FE FF     UTF-32/UCS-4, big-endia

发现问题解决就很容易了,查找删除BOM就OK了,linux下BOM相关的命令有:

VIM的BOM操作

复制代码 代码如下:


#添加BOM
:set bomb
#删除BOM
:set nobomb
#查询BOM
:set bomb?

查找UTF-8编码中的BOM

复制代码 代码如下:

grep -I -r -l $'\xEF\xBB\xBF' /path


还可以在svn的钩子中禁止提交BOM(以下代码来自网络,没校验)

复制代码 代码如下:


#!/bin/sh

REPOS="$1"
TXN="$2"

SVNLOOK=/usr/bin/svnlook

FILES=`$SVNLOOK changed -t "$TXN" "$REPOS" | awk {'print $2'}`

for FILE in $FILES; do
    CONTENT=`$SVNLOOK cat -t "$TXN" "$REPOS" "$FILE"`

    if echo $CONTENT | head -c 3 | xxd -i | grep -q '0xef, 0xbb, 0xbf'; then
        echo "BOM!" 1>&2
        exit 1
    fi
done


最后提醒大家在wowdows下最好别使用记事本等会自动添加BOM的编辑器修改代码,容易引发一些问题。
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